Where is your research on this? From what I see is that almost all the big sellers, Mandrake, Redhat (Even though they use blue curve) Xandros, Linspire etc use KDE by default.

Only Ubuntu (Who know have put KUbuntu in to the main code base because KDE was so popular) and Novell (Who changed their minds real quick on making Gnome the default UI) And Novell was just thinking about costs cause they own Gnome, but found out they would loose a bunch of users or Open Suse would be forked for KDE users!